"There was a series of math books, which started Arithmetic for the Practical Man, and then Algebra for the Practical Man, and then Trigonometry for the Practical Man, and I learned trigonometry for the practical man from that. I soon forgot it again because I didn't understand it very well but the series was coming out, and the library was going to get Calculus for the Practical Man and I knew by this time by reading the Encyclopedia that calculus was an important subject...and then the calculus book finally came out ...and I went to the library to take it out and she looks at me and she says, "Oh, you're just a child, what are you taking this book out for, this book is a [book for adults]." So this was one of the few times in my life I was uncomfortable and I lied and I said it was for my father, he selected it. So I took it home and I learnt calculus from it..."
Calculus for the Practical Man was first published in 1931 when Feynman was about 13 years old, which fits the story (he was waiting for the book's publication).
So that would point to Feynman's calculus book being "Calculus for the Practical Man" by J.E.Thompson rather than Silvanus P Thompson's "Calculus Made Easy", whose second edition came out in 1914. I would not be surprised that Feynman read and used both.
The two books are quite different in approach, Practical having, to me, a rather unique physics orientation and being a more demanding text.
It's just that the quote on fools is very prominent in the beginning of Calculus Made Easy, and the author continues to hilariously refer to both other people and himself as fools. I searched inside Calculus for the Practical Man  on archive.org for the word "fool" without a single hit.
I'm sure Feynman read both, but I was interested in the origin of the quote, since I learned it a few days ago and think it's very inspirational. Feynman was constantly arguing that everyone has the capacity to figure things out, it's just that they rarely practice it.
As I continued reading I found the relevant quote to the second text, Calculus Made Easy, on page 194 of Feynman's "The Pleasure of Finding Things Out", where Feynman states:
"I had a calculus book once that said, 'What one fool can do, another can.'"
While he doesn't name it, that's almost without a doubt "Calculus Made Easy". Both calculus texts are thus referred to in Feynman's "The Pleasure of Finding Things Out". In the index of that book, under the topic "Calculus", the pages of both references can be found.
To wit: hardcover & softcover copies of both are rather expensive (at least in Canada). If they're in any good shape they run ~$50 to ~$80.
Kindle has them both for $6 and change.
What an interesting world we would live in if there really were a plural of Feynman. :-)